The present invention relates to a device, or appliance, for styling or shaping the hair comprising a handle joined to a retaining part and a heating part between which a lock of hair may be inserted, more particularly a device comprising a mechanism for exerting pressure on the lock of hair to be treated.
Most hair-shaping devices, for example straightening, curling and crimping irons, comprise a handle supporting two mechanical elements, at least one of which is heated, the other element being provided for bringing the hair into contact with the first one, particularly by moving from an open position that allows the hair to be inserted to a closed position that places it in contact with the heating part. The movement from the open position to the closed position is produced manually by pressing on an opening lever of a clip that exerts pressure on the hair or by pressing two articulated arms of the device toward one another so as to bring the heating part in contact with the hair. The problem encountered with such devices is that, because they pivot about an axis of rotation that is at a distance from the treatment part, they do not provide uniform contact pressure on the hair.
The quality of heat-shaping of the hair is determined by the laws of heat transfer and depends on parameters such as the contact time, the temperature of the heat exchange, the diffusivity of the materials, the mass of the elements, and the quality of the contact.
The document EP 1 030 571 proposes a device that provides better contact between a cylindrical heating mandrel and the hair to be treated by using a pressure piece that is spring-mounted on the pivoting support clip for retaining the hair. This type of pivoting clip with a spring-mounted pressure piece increases the size of the device in the radial direction and thus only makes it possible to produce curls of fairly large diameter. Moreover, the pressure piece and the support clip are joined by a mechanical link embodied by the spring, this link being subject to friction in operation and giving rigidity to the assembly, which therefore cannot effectively adapt to fine locks of hair.
The document JP 2000-333719 proposes a similar solution in a hair-straightening device comprising two jaws, pivotably mounted about an end joint, wherein one of the jaws comprises a heating straightening plate mounted so as to be fixed relative to its support, the opposing jaw comprising a straightening plate mounted so as to be movable relative to its support in the jaw, under the pressure of a spring. The same size problem arises in the device of this document, the plates of which must be fairly thin in order for a user to be able to close them easily with one hand. Moreover, the reliability of spring-mounted pressure plates is questionable, since the spring can jam, or even break, in operation.
Similar solutions are described in other documents such as JP 2002-291517 and JP2003-250626, wherein the devices use other types of springs to produce a float-mounting of the heating plates. More particularly, the device described in the document JP2003-250626 comprises straightening plates, each of which is float-mounted by means of leaf springs on the end of a jaw, the jaws themselves being pivotably articulated at the other end in order to provide an open position and a closed position of the device. Each straightening plate comprises a magnet that cooperates with the magnet of the opposing straightening plate to guarantee the parallelism of the plates when the device is closed. These devices using a floating spring mount have the same drawbacks as those mentioned above.